This invention relates to the field of pressure lock terminals for electrical receptacles wherein the bared end of a wire conductor is inserted into a recess of the receptacle for electrical connection therewith, and it becomes locked therein until released.
Prior art devices of this type have used various types of cantilevered spring members formed from the conductive bus element of the receptacle to bear against one side of an inserted wire conductor, and an oppositely facing bearing wall or anvil also formed from the conductive bus element to bear against the second opposite side of the inserted wire conductor.
One problem encountered by such prior art devices was skewing of the inserted wire conductor away from the free end of the cantilever spring with resultant loss of electrical contact, creation of a high resistance connection, and weakening or complete loss of the mechanical connection whereby the wire conductor could be accidentally withdrawn entirely from the receptacle leaving a bared end of the conductor exposed.
Another problem encountered by prior art devices is the inability to receive various sized diameter conductors through a plug-in aperture in the back of the receptacle without causing a permanent set to occur in the spring when a relatively large conductor is inserted through the aperture. A permanent set occurs in the spring when a conductor having a large diameter is inserted and the size of the diameter of the conductor causes the spring to deflect beyond its elastic limits thus resulting in a spring which does not return to its original position after the conductor is withdrawn. Existing prior art devices have a single action cantilever spring, and in order to adapt such springs for a wide range of various diameters of conductors, a relatively large lever arm to obtain the magnitude of deflection is needed to accommodate a wide range of conductor diameters without causing a undesirable permanent set to occur.
The novel invention of the above-identified copending application solves the problem of skewing by providing a recess having a continuous bounding wall in which the inserted bared end of the wire conductor seats. The wire conductor is thus held against skewing and is retained in alignment with the free end of the cantilever spring which biases the wire conductor against an oppositely facing anvil or bearing wall which extends longitudinally from the recess having a completely bounding wall to the opening to the exterior surface of the receptacle. The anvil or bearing wall is provided with a concave bearing face throughout its longitudinal extent, to bear against and support a substantial portion of the circumference of the bared wire conductor throughout its full inserted length. Thus, in addition to the fully bounded wall of the seat which positively retains the end of the inserted wire conductor from skewing, the concave surface of the anvil or bounding wall provides a trough which also retains the inserted wire conductor from skewing. To accomplish these objectives the fully bounded seat and the concave anvil wall are formed as depending members of the cover portion of the receptacle.
The novel invention of the above-identified copending application provides a receptacle which is adapted to receive various diameter size conductors by using a double action spring which enables the spring to deflect over a wide range to accommodate differing conductor diameters.
A drawback of the spring disclosed in the above identified copending application is the lack of a high degree of structural strength. It was believed that it was necessary to sacrifice a certain amount of structural strength in order to achieve the novel double action spring mechanism. The present invention surprisingly achieves this double action spring mechanism without a loss of structural strength.